1. Field of the Invention
The present invention relates to a backlight device excellent in irradiation characteristics and a transmission type display apparatus excellent in display characteristics.
2. Description of the Related Art
There is disclosed a display apparatus in which light sources are disposed at different two light-incident end surfaces of a light guide plate, respectively, a double-sided prism lens sheet having a triangular prism row and a cylindrical lens row is disposed on the light outgoing surface side of the light guide plate, and a transmission type display panel is disposed on the light outgoing surface side of the prism sheet. According to the display apparatus, light rays emitted from the light sources are irradiated from the transmission type display panel at angles corresponding to parallax of left and right eyes, respectively, and parallactic images are alternately displayed on the transmission type display panel in synchronous with the light sources, whereby a three-dimensional display can be realized (see WO 2004/027492 A1, for example).
Further, there is disclosed a liquid crystal display apparatus using a liquid crystal display panel in which a parallax barrier layer and an image forming layer including a liquid crystal layer are provided via a transparent layer. According to the liquid crystal display apparatus, the distance between the image forming layer and the parallax barrier layer is adjusted to a distance suitable for the double image display. Thus, an image for a left side viewer and an image for a right side viewer formed on the image forming layer are conducted to the left side viewer and the right side viewer by transmission lights passed through the parallax barrier, respectively, whereby the double image display for displaying different images can be realized (see JP-A-2005-258016, for example).
According to the display apparatus shown in WO 2004/027492 A1, when two different images are repeatedly rewritten on the liquid crystal panel in synchronous with the changing-over of the lighting of the light sources disposed at the different two light-incident end surfaces of the light guide plate, it is possible to show different images to a user viewing in a range from the normal line direction of a display screen to 15 degrees to the left side therefrom and a user viewing in a range from the normal line direction to 15 degrees to the right side therefrom, respectively. However, when a main user sits just in front of the display panel, there arises a problem that two images are displayed in a mixed manner in the front direction.
Further, according to the display apparatus shown in JP-A-2005-258016, an image for a left side viewer and an image for a right side viewer are displayed on the image forming layer, and the parallax barrier is set so that the light rays emitted from the respective images are conducted to the left side viewer and the right side viewer, respectively. Thus, since the display angles are set to oblique angles, there arises a problem that the usability is not good when a user sits just in front of the display panel. Further, since the image forming layer is divided into two for a left side viewer and a right side viewer, respectively, there arises a problem that the number of pixels of an image being displayed becomes half. Further, since the transmission light is partially shielded by the parallax barrier, there arises a problem that the display becomes dark.